ath79: prepare NAND subtarget for upstream support of SPI NAND

Linux 4.19 supplies the upstream spi-nand framework,
permitting porting and support of boards with SPI NAND.

  * Adjusted nand/target.mk to provide FEATURES += squashfs nand

  * Updated config-default to provide current MTD and UBI support

Defaults selected for:

  CONFIG_MTD_UBI_WL_THRESHOLD=4096
  CONFIG_MTD_UBI_BEB_LIMIT=20
  # CONFIG_MTD_UBI_FASTMAP is not set
  # CONFIG_MTD_UBI_GLUEBI is not set

The bad-block reservation limit technically should be 21 for Paragon
SPI NAND but most other devices in the class are 20 blocks per Gbit.
In Linux 5.2 this is specified on a per-chip basis through NAND_MEMORG

Contents adjusted to remove declarations provided at the target level
by commit 08a134820f5 (Oct 23, 2019) ath79: enable PCI for whole target

Signed-off-by: Jeff Kletsky <[email protected]>
Tested-by: Michal Cieslakiewicz <[email protected]>

target/linux/ath79/nand/config-default

@@ -1,18 +1,17 @@
-CONFIG_AT803X_PHY=y
-CONFIG_BCH=y
 CONFIG_MTD_NAND=y
 CONFIG_MTD_NAND_AR934X=y
-CONFIG_MTD_NAND_BCH=y
+CONFIG_MTD_NAND_CORE=y
 CONFIG_MTD_NAND_ECC=y
-CONFIG_MTD_NAND_ECC_BCH=y
-CONFIG_MTD_SPINAND_MT29F=y
-CONFIG_MTD_SPINAND_ONDIEECC=y
+CONFIG_MTD_SPI_NAND=y
 CONFIG_MTD_UBI=y
-CONFIG_MTD_UBI_BEB_LIMIT=20
 CONFIG_MTD_UBI_BLOCK=y
+CONFIG_MTD_UBI_WL_THRESHOLD=4096
+CONFIG_MTD_UBI_BEB_LIMIT=20
 # CONFIG_MTD_UBI_FASTMAP is not set
 # CONFIG_MTD_UBI_GLUEBI is not set
-CONFIG_MTD_UBI_WL_THRESHOLD=4096
+# CONFIG_PCI_AR71XX is not set
+# CONFIG_PHY_AR7100_USB is not set
+CONFIG_PHY_AR7200_USB=y
 CONFIG_UBIFS_FS=y
 CONFIG_UBIFS_FS_ADVANCED_COMPR=y
 CONFIG_UBIFS_FS_LZO=y

target/linux/ath79/nand/target.mk

@@ -1,9 +1,10 @@
 BOARDNAME := Generic devices with NAND flash
-FEATURES += squashfs nand rtc
+
+FEATURES += squashfs nand
 
 DEFAULT_PACKAGES += wpad-basic
 
 define Target/Description
-	Build firmware for Atheros AR71xx/AR913x based boards with
-	NAND flash, e.g. Netgear WNDR4300.
+	Firmware for boards using Qualcomm Atheros, MIPS-based SoCs
+	in the ar72xx and subsequent series, with support for NAND flash
 endef